Land mine expulsion system

ABSTRACT

In an air-delivered land mine, a system for expelling an explosive warhead from beneath the ground including an inner cylindrical shell containing an explosive material, the inner shell being concentrically positioned within an outer cylindrical shell which itself has an outer aerodynamic configuration. A rocket engine which functions as both a gas generator and thruster is fixed to an end of the inner shell actuatable in response to an influence sensor. The inner shell is fixed to the outer shell at an annular flange by a retaining ring whose threads are sheared when sufficient pressure is generated by the actuated rocket engine. Subsequently, the rocket engine thrusts the inner shell from the outer shell to a position above the ground whereupon a suitable device, such as a lanyard whose ends are connected to the inner shell and to a firing switch located on the outer shell, initiates the explosive at a predetermined height.

United States Patent Faulstich, Jr. et a1.

[451 Nov. 25, 1975 Primary Examiner-Verlin R. Pendegrass Attorney, Agent, or Firm-R. S. Sciascia; .1. A. Cooke [57] ABSTRACT In an air-delivered land mine, a system for expelling an explosive warhead from beneath the ground including an inner cylindrical shell containing an explosive material, the inner shell being concentrically positioned within an outer cylindrical shell which itself has an outer aerodynamic configuration. A rocket engine which functions as both a gas generator and thruster is fixed to an end of the inner shell actuatable in response to an influence sensor. The inner shell is fixed to the outer shell at an annular flange by a retaining ring whose threads are sheared when sufficient pressure is generated by the actuated rocket engine. Subsequently, the rocket engine thrusts the inner shell from the outer shell to a position above the ground whereupon a suitable device, such as a lanyard whose ends are connected to the inner shell and to a firing switch located on the outer shell, initiates the explosive at a predetermined height.

3 Claims, 3 Drawing Figures 1 1 LAND MINE EXPULSION SYSTEM (75] Inventors: Albert J. Faulstich, Jr., Silver Spring; Richard L. Hargett, Frederick, both of Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: June 15, 1971 21] Appl. No.: 154,239

[52] [1.8. CI 102/8; 89/1.806 [51] Int. Cl. F42b 23/00 [58] Field 01 Search..... 102/72, 8; 89/1.816, 1.817, 89/1.818, 1.806, 1.807

[56] References Cited UNITED STATES PATENTS 1,235,637 8/1917 Barlow 102/7.2 1,239,134 9/1917 Steel 102/192 1,317,608 9/1919 Barlow 102/7.2 1,791,716 2/1931 Davis et al. 102/7.2 3,072,022 1/1963 Wood et a1. 89/1.806 3,195,459 7/1965 Reed,.1r 102/72 3,326,128 6/1967 Choate 89/1.8l8 X 3,398,639 8/1968 Apotheloz 89/1.807

FOREIGN PATENTS OR APPLICATIONS 1,182,275 2/1970 United Kingdom 89/1.806

Sheet 1 of2 Patent Nov. 25, 1975 Fig. 2

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Sheet 2 of 2 US. Patent Nov. 25, 1975 .wd F

LAND MINE EXPULSION SYSTEM 2 BACKGROUND OF THE INVENTION This invention relates generally to expulsion systems, and more particularly to apparatusfor expelling the warhead of an ordnance item from below to above the surface of the ground prior to explosive initiation.

In the past, air delivered land mines have been adapted to completely bury themselves in the ground upon impact. It has been the practice in the use of these mines to provide conventional influence sensors such, for example, as magnetic sensors, in order to explosively initiate the mine in response to appropriate ex ternal stimuli. It has been found, however, that the cult, but is disadvantageous in that the lethal radius of such a mine is greatly limited. Therefore, various apparatus have been developed for the purpose of expelling buried mines from beneath the ground to a position above the ground, prior to detonation thereby combining the advantages of a buried land mine, i.e. difficulty of recognition by the enemy, and advantages of surface planted land mines, i.e. increase in lethal effectiveness.

Systems developed to. expel ordnance from the ground have been investigated. In particular, apparatus has been developed capable of expelling the entire unit clear of the ground. However, problems have arisen with apparatus of this type. For example, due to the high velocity at impact, the outer shell-of an air-delivered mine effectively becomes welded to the soil in which it is buried. Therefore, the frictional forces holding the side of the ordnance device in the ground are high and quite unpredictable. Accordingly, the amount of energy required for expulsion is extremely difficult,

if not impossible, to predict. Another problem inherent in entire unit-expulsion systems is that very often gas I generators are provided on the nose of the ordnance item. Upon actuation, the generated gas vents into the soil and it is not uncommon for little or no pressure to be built up due to the looseness of the soil and consequent escape of the gases. As stated above, the amount of energy necessary to overcome the extremely high friction forces of the ground on the weapon is ex- ,tremely large, and; accordingly, an excessive percent- !age of the overall weapon size would be required to house an explusion system capable of generating the required energy. Thus, a need exists for an efficient and I 1 practical means for expelling buried ordnance from the vide'a new and improved expulsion system for buried ordnance.

Another object of the invention is the provision of a new and improved expulsion system which requires relatively small amounts of energy to operate.

' Still another object of the present invention is to provide a new and improved expulsion system which takes up a relatively small percentage of the overall weapon size.

A further object of the instant invention is to provide a new and improved expulsion system wherein the explosively laden warhead is expelled from the ground in a shotgun fashion utilizing other mine apparatus as a gun bore. A

A still further object of the instant invention is to provide an expulsion system for buried mines capable. of launching a warhead to a predetermined height.

Briefly, in accordance with one embodiment of this invention, these and other objects are attained by providing in an air delivered land mine, adapted to bury itself beneath the surface of the ground, a pair of concentric cylindrical shells, the outer one of which is closed at an end comprising the nose portion of the mine while the inner shell provides a housing for the explosive material. A gas generator is provided within the closed end portion of the outer shell and may be connected to the end of the inner shell adjacent thereto. After penetration into the ground, the outer shell re mains in the ground and serves as a smooth bore for the inner shell which is expelled therefrom upon actuation of the gas generator by conventional influence sensors.

BRIEF DESCRIPTION OF THE DRAWING A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a side view in partial section of the mine in the buried configuration;

FIG. 2 is an enlarged side view in partial section of a portion of the mine; and

FIG. 3 is a side view of the mine in partial section wherein the mine is in operation.

DESCRIPTION OF THE- PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof, the land mine generally denoted at 10, includes an elongate, generally cylindrical outershell 12. The shell 12 is closed at one end by a cone-shaped, tapered end portion 14 and open at the other end. The tapered end portion 14 provides a suitable terradynamic configuration as will be discussed hereinafter. Substantially adjacent to the lower end portion 14, an annular flange I6 is formed along the interior wall 18 of the outer shell 12. The interior wall 18 serves as a smooth barrel during the expulsion of the inner shell, described in greater detail hereinafter. An elongate cylindrical inner shell 20 having a diameter slightly smaller than the inner diameter of outer shell 12 is concentrically positioned therein. The inner shell 20 provides a housing for suitable explosive material 22 (see FIG. 2). Transversely positioned at the upper end of the inner shell are elongate members 15 which serve as terrabrakes, i.e. facilitate the deceleration of the mine upon ground impact.

Referring to FIG. 2, the lower end of inner shell has integrally formed thereon a rocket motor which has sufficient thrust capabilities to lift the inner shell and material housed therein to a predetermined height. The rocket motor 24 is connected to the inner shell by an integral reduced diameter partially threaded intermediate portion 26. A shoulder 28 is defined on inner shell 20 by the intersection of the intermediate portion 26 and the lower end of inner shell 20. When positioning the inner shell 20 within outer shell 12, shoulder 28 bears against the upper surface of flange 16 and intermediate portion 26 and rocket motor 24 fits through the opening defined by flange 16. The intermediate portion 26 is of sufficient length to enable the lower portion thereof to protrude beyond the lower surface of flange l6 and also includes an O-ring 27 positioned in an annular groove formed therein providing gas sealing means for fluidly sealing the tapered end portion from the remainder of the shell. Thus, it is seen that the rocket motor 24 extends into a closed chamber 32 defined by the inner walls of the tapered end portion of the outer shell. An internally threaded retaining ring 30 is threaded onto the protruding portion of intermediate portion 26 and is threaded tightly against the lower surface of flange 16 so as to rigidly fasten the inner shell and explosive contained therein thereto. The retaining ring is formed of a metal such, for example, as aluminum for purposes which will become clearer in the discussion of the operation of the invention.

In operation, the mine is launched from an aircraft and due to a suitable aerodynamic configuration, attains a near vertical trajectory prior to ground entry. Upon entering the ground, the mine is buried as shown in FIG. 1. Conventional influence sensors are provided (not shown) which, upon monitoring the appropriate external conditions, actuate the rocket motor 24. The rocket motor for a limited period of time acts as a conventional gas generator until sufficient pressure is generated within the chamber 32 defined by end portion 14 to cause the threads formed on retaining ring 30 to shear. The energy level required for such shearing is relatively predictable since the pressure required for ejection is a function of the shear resisting capability of the retaining ring alone which may be determined by appropriate engineering formulae. After the shearing of the threads, there is nothing to prevent the inner shell 20 from being expelled, as shown in FIG. 3, from the outer shell 12 which acts as a smooth bore barrel therefore. Annular rings 34 formed of a smooth material such, for example, as Teflon, are provided at spaced intervals along the inner surface of the outer shell 12. These rings prevent any possible binding of the inner shell as it travels upwards along the outer shell 12. The inner shell 20 rises sustained by the rocket motor 24 which now serves as a conventional rocket motor. At a predetermined height, a device, such for 4 example, as a lanyard (not shown), mutually connecting the inner and outer shell, initiates the explosive.

Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings. For example, the expulsion system described need not be limited to land mines, but may be utilized in underwater mines buried in the sea bottom and in launch systems for expelling missiles from silos. Further, a rocket engine need not be used, but rather a conventional gas generator positioned within chamber 32 may be employed to expel the explosive carrying inner shell from within the outer shell. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An air-delivered, mine expulsion system comprising:

an elongated, cylindrical outer shell having a closed end portion for penetration into the ground;

an elongated inner shell positioned within said outer shell;

a rocket motor integrally fixed to one end of said inner shell and extending into a chamber defined within said end portion of said outer shell for expelling to a predictable height of said inner shell from said outer shell in response to predetermined influences;

gas sealing means between said outer and said inner shells for fluidly sealing said chamber from the remainder of said outer shell;

elongated brake members transversely positioned on the other end of said inner shell to control deceleration upon ground impact; and

means for retaining said inner shell within said outer shell and for releasing said inner shell a short time after actuation of said rocket motor including:

an annular flange formed along the interior of said outer shell approximate said closed end portion; threaded portion formed on said inner shell forwardly of said rocket motor which extends through the opening formed by said flange; and

a shearable retaining ring threadedly cooperating with said threaded portion and bearing on the after surface of said flange.

2. A system as recited in claim 1 further comprising a plurality of annular rings of smooth material circumferentially positioned at intervals around said inner shell to facilitate expulsion of said inner shell from said outer shell.

3. A mine as recited in claim 1 wherein said retaining ring is formed of aluminum. 

1. An air-delivered, mine expulsion system comprising: an elongated, cylindrical outer shell having a closed end portion for penetration into the ground; an elongated inner shell positioned within said outer shell; a rocket motor integrally fixed to one end of said inner shell and extending into a chamber defined within said end portion of said outer shell for expelling to a predictable height of said inner shell from said outer shell in response to predetermined influences; gas sealing means between said outer and said inner shells for fluidly sealing said chamber from the remainder of said outer shell; elongated brake members transversely positioned on the other end of said inner shell to control deceleration upon ground impact; and means for retaining said inner shell within said outer shell and for releasing said inner shell a short time after actuation of said rocket motor including: an annular flange formed along the interior of said outer shell approximate said closed end portion; a threaded portion formed on said inner shell forwardly of said rocket motor which extends through the opening formed by said flange; and a shearable retaining ring threadedly cooperating with said threaded portion and bearing on the after surface of said flange.
 2. A system as recited in claim 1 further comprising a plurality of annular rings of smooth material circumferentially positioned at intervals around said inner shell to facilitate expulsion of said inner shell from said outer shell.
 3. A mine as recited in claim 1 wherein said retaining ring is formed of aluminum. 